Abstract

In this paper, we proposed a novel concatenated coded modulation composed of adaptive turbo code with trellis-coded modulation (ATTCM) that is based on generalized frequency division multiplex (GFDM) system. The proposed scheme has low complexity and provides high spectrum efficiency and significant coding gain. An experiment with 4 Gbit/s novel concatenated coded modulation GFDM system is successfully demonstrated with the proposed method. It is shown that the novel concatenated coding modulation signal (ATTCM 32QAM) provides 2.3 dB coding gain over that of TCM32QAM signal at bit error rate of 1e–3. This paper indicates a prospect solution for the future fifth generation optical access system.

Introduction

At present, the dramatic growth of services demands of the optical fiber communication increases rapidly. Optical access network is a strong candidate for connecting the backbone network with the end users, which provides high speed and high reliability for bandwidth hungry applications [1], [2].Currently commercial access systems mainly apply lean single carrier, However, the increasing demands of users are pushing forward to extend bandwidth resources, the multicarrier technology has been proposed in the past few years, fourth generation (4G) cellular systems based on OFDM technology have been optimized to provide high data rates and reliable coverage to mobile users [3]. Nevertheless, OFDM is susceptible to inter-carrier interference and synchronization errors. Additional overhead such as cyclic prefix (CP) is needed to alleviate the interference [3]. While generalized frequency division multiplexing (GFDM) based on multicarrier filter bank is a strong modulation technique for the fifth generation (5G) standard [4]–[7]. The main characteristic of GFDM is low out of band emission, insensitive to frequency offset and phase noise. Cyclic prefix is added to each GFDM block instead of each GFDM symbol. The peak-to-average power ratio (PAPR) can be reduced by designing the flexible pulse shaping of individual subcarriers [6], [7]. In addition, GFDM technology with high spectral efficiency enables the access system to support a huge number of optical network units. They are more susceptible to transmission impairments from channel and components in optical access network, which leads to inter-symbol interference (ISI) and degrade the performance of the system [6]. Therefore, the forward error correction (FEC) codes can be employed to improve the BER performance by providing extra gain to the optical access network; it is a powerful technique to increase the system’s margin [8]–[10]. Turbo code as one of the FEC code, has very good performance for error correction. It not only has superior performance in high noise environment, but also has strong anti-fading and anti-interference ability. Moreover, the ability to provide communication near the shannon limit in various harsh conditions has been demonstrated. Turbo code has been as deep space communication standard by the United States advisory committee of space data system which provides an important background for the research of Turbo code implementation [11]. However, Turbo code has the problem of error floor, this phenomenon will seriously affects the high reliability in the actual communication. While the technology of combing turbo code with trellis coded modulation (TCM) can improve spectrum efficiency and has robust error correction quality with simple construction where the error floor problem can be avoided, which makes it an attractive solution for optical access network in the near future [12]–[16]. In this paper, we propose and experimentally demonstrate a novel concatenated coded modulation (adaptive turbo trellis-coded modulation (ATTCM)) in 4 Gbit/s GFDM optical access system. The code weight decision algorithm (CWD) is used for adaptive code. The decoder of ATTCM used Log-MAP algorithm and reduced the complexity of the receiver. By combing these techniques, the proposed scheme provides significant performance improvement for access system.

چکیده

در این مقاله، ما یک مدولاسیون کدگذاری شده زنجیره‌ای نوین که از ترکیب کد توربو تطبیقی با مدولاسیون کدگذاری مدور (ATTCM) ساخته شده و مبتنی بر سیستم تقسیم فرکانس کلی (GFDM) می‌باشد را ارائه داده‌ایم. طرح پیشنهاد شده دارای پیچیدگی کمتر بوده و کارایی طیفی زیاد و بهره‌ی کدگذاری قابل توجهی را فراهم می‌آورد. یک آزمایش با سرعت 4 گیگابیت بر ثانیه، سیستم مدولاسیون کدگذاری شده زنجیره‌ای نوین مبتنی بر GFDM را توسط طرح پیشنهادی با موفقیت نشان داده است. در این مقاله همچنین نشان داده شده‌است که سیگنال مدولاسیون کدگذاری شده زنجیره‌ای نوین (ATTCM32QAM) در نرخ خطای بیت 3-1 بهره‌ی سیگنال 3/2 دسی‌بل را بر روی سیگنال TCM32QAM ایجاد می‌کند. این مقاله یک راه‌حل امیدوارانه برای سیستم دسترسی نوری در نسل پنجم ارتباطات در آینده را نشان می‌دهد.

مقدمه

در حال حاضر، رشد چشمگیر سرویس‌ها و خدمات باعث افزایش سریع ارتباط فیبر نوری شده‌است. شبکه‌ی دسترسی نوری یک گزینه‌ی مناسب و قوی برای اتصال شبکه‌ی اصلی با کاربران انتهایی است که سرعت بالا و قابلیت اطمینان زیادی را برای برنامه‌های کاربردی نیازمند پهنای‌باند فراهم می‌کنند [1] و [2].

2- مدل اصلی سیستم 

بلوک دیاگرام مدولاسیون کدگذاری شده زنجیره‌ای GFDM در شکل 1 نشان داده شده‌است. این بلوک دیاگرام از مدولاسیون ATTCM و GFDM تشکیل شده‌است. اصول مربوط به هر قسمت در بخش زیر توضیح داده شده‌است.

The modelling and dynamic analysis of shell and tube heat exchangers will be considered in this contribution. Procedures which incorporate the heat transfer and the fluid flow system properties, for these processes, will be developed. An incremental, energy balance yielding the system, partial differential equations presents the governing process. The multivariable, multi-dimensional, Laplace transformed, distributed parameter formulation of heat exchanger representations, are provided. A frequency domain description of the system model is derived enabling the recovery of Laplace function rationality for both parallel and counter flow heat exchanger models. Suitable feedback control techniques are identified, as a prelude to closed loop design studies. The dynamics, for tubular heat exchangers are computed, for purposes of comparison with alternative response and regulation approaches. A typical application study is outlined.

Introduction

Heat exchangers are used in many industries where fluid heat transfer is required, see for example Saunders E.A (1). In this operation heat energy is transferred from a hot to a cooler fluid flow stream by a carrier type, energy conversion process, as in Hewitt G et al (2) and Coulson. H. G and Richardson J. (3). This involves coupled fluid flow and thermal interactions where heat is transferred along with the fluid flow through the containing volumes and across the separating, heat exchanger, tube walls. The heating of materials during conveyancing operations would also be equivalent to a carrier flow, heat transfer, percolation process. Continuous conveyor fed food preparation systems and the fluid drainage from the pulp-fibre suspensions, in the paper and board manufacturing industries, as detailed in Smith B.W (4), for example, also comprise percolation, heat and mass transfer processes. However, in this compilation the large scale, tubular heat transfer units commonly employed in the oil, gas and chemical industries, as discuss in Sadik K and Liu H. (5), and Smith E.M (6) will be the focus of the formulation, analysis and simulation studies presented herein. These devices are also used in ventilation, air conditioning and battery cooling systems, as detailed in Whalley R and Ameer A (7), Roetzel, W. and Xuan, Y. (8) in refrigeration units, in fossil fuel boilers, see for example Whalley R (9) and in nuclear, electrical power generation plant, as shown in Schultz M.A. (10). Generally, tubular heat transfer units are configured to work in series with a fluid source of supply and a suitable coolant or heating, fluid stream. A continuous process is employed thereafter to simultaneously achieve, the parallel or counter flow, heating or cooling effect required.